This invention relates to a motor vehicle brake pedal for an electronic or xe2x80x9cbrake-by-wirexe2x80x9d braking system which includes a brake pedal feel emulator which artificially mimics or emulates the pedal feel of a traditional hydraulic braking system.
Early motor vehicles were equipped with hydraulic braking systems in which a master cylinder was directly actuated by a brake pedal to operate the vehicle brakes. The force applied by the operator to the brake pedal was opposed by a force generated by the hydraulic force applied to the vehicle brakes. This force initially increased quite slowly because compliance in the hydraulic system and in the brakes had to be taken up and the force of return springs of drum brakes had to be overcome. After this initial phase, the force applied to the brake pedal is increased at an exponential rate. Vehicle operators are accustomed to this pedal xe2x80x9cfeelxe2x80x9d characteristics of manual braking systems and expect all braking systems to react in the same way. For example, when power assisted brakes were introduced, the power booster had to incorporate the feel of the prior manual braking systems in order to be acceptable to vehicle operators.
More recently, electronic or xe2x80x9cbrake-by-wirexe2x80x9d braking systems have been proposed. In such systems, braking is generated by an electro-hydraulic system in which the brake pedal generates an electrical signal which controls an electronic controller which controls the operation of a pump that applies the vehicle brakes, or the brakes include an electric motor which is controlled by the signal transmitted to the electronic controller by the brake pedal. Accordingly, these electronic braking systems must incorporate a pedal which provides xe2x80x9cfeelxe2x80x9d to the vehicle operator that emulates the feel vehicle operators are accustomed to as described above. Prior art brake pedal feel emulators are disclosed in U.S. Pat. Nos. 5,729,979 and 5,603,217.
According to the present invention, a single cantilever spring reacts against a shaped surface and is mounted such that the free end thereof applies a force to the brake pedal which varies as the point at which the spring diverges from the shaped surface changes in response to movement of the brake pedal. The free length of the spring is therefor varied as the pedal is depressed as a function of the shape of the shaped surface, so that the feedback force applied to the pedal may be designed to vary to emulate the feel of a conventional braking system.